Rounding creatinine, cystatin C or both: impact on discordance group assignment and GFR-estimating equation performance

Groothof, Dion; Shehab, Naser B N; Post, Adrian; Gans, Reinold O B; Bakker, Stephan J L; Erler, Nicole S

doi:10.1093/ndt/gfad224

Cited by 2 publications

(3 citation statements)

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“…Discordant values can arise from various sources, such as rounding of or measurement errors in creatinine or cystatin C levels, assumptions underlying GFR-estimating equations, and (unidentified) factors accounting for variability in creatinine and cystatin C unrelated to GFR, referred to as 'non-GFR determinants'. 38 A recent study that leveraged real-world data suggested that the estimating equation that combines both markers (eGFRcr-cys) is more accurate than either eGFRcr or eGFRcys in cases of high discordance. 39 A major limitation of the study was the lack of data on why patients were referred for assessment of creatinine, cystatin C, and measured GFR, which both hampered determining the more accurate eGFR and appraisal of the extent to which non-GFR determinants may have confounded results.…”

Section: Discussionmentioning

confidence: 99%

“…In such cases, it becomes challenging for physicians to determine which value is more trustworthy. Discordant values can arise from various sources, such as rounding of or measurement errors in creatinine or cystatin C levels, assumptions underlying GFR‐estimating equations, and (unidentified) factors accounting for variability in creatinine and cystatin C unrelated to GFR, referred to as ‘non‐GFR determinants’ 38 . A recent study that leveraged real‐world data suggested that the estimating equation that combines both markers (eGFRcr‐cys) is more accurate than either eGFRcr or eGFRcys in cases of high discordance 39 .…”

Section: Discussionmentioning

confidence: 99%

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Creatinine, cystatin C, muscle mass, and mortality: Findings from a primary and replication population‐based cohort

Groothof,

Shehab,

Erler

et al. 2024

J cachexia sarcopenia muscle

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BackgroundSerum creatinine is used as initial test to derive eGFR and confirmatory testing with serum cystatin C is recommended when creatinine‐based eGFR is considered less accurate due to deviant muscle mass. Low muscle mass is associated with increased risk of premature mortality. However, the associations of serum creatinine and cystatin C with muscle mass and mortality remain unclear and require further investigation to better inform clinical decision‐making.MethodsWe included 8437 community‐dwelling adults enrolled in the Dutch PREVEND study and 5033 in the US NHANES replication cohort. Associations of serum creatinine and/or cystatin C with muscle mass surrogates and mortality were quantified with linear and Cox proportional hazards regression, respectively. Missing observations in covariates were multiply imputed using Substantive Model Compatible Fully Conditional Specification.ResultsMean (SD) age of PREVEND and NHANES participants (50% and 48% male) were 49.8 (12.6) and 48.7 (18.7) years, respectively. Median (Q1–Q3) serum creatinine and cystatin C were 71 (61–80) and 80 (62–88) μmol/L and 0.87 (0.78–0.98) and 0.91 (0.80–1.10) mg/L, respectively. Higher serum creatinine was associated with greater muscle mass, while serum cystatin C was not associated with muscle mass. Adjusting both markers for each other strengthened the positive relationship between serum creatinine and muscle mass and revealed an inverse association between serum cystatin C and muscle mass. In the PREVEND cohort, 1636 (19%) deaths were registered over a median follow‐up of 12.9 (5.8–16.3) years with a 10‐year mortality rate (95% CI) of 7.6% (7.1–8.2%). In the NHANES, 1273 (25%) deaths were registered over a median follow‐up of 17.9 (17.3–18.5) years with a 10‐year mortality rate of 13.8% (12.8–14.7%). Both markers were associated with increased mortality. Notably, when adjusted for each other, higher serum creatinine was associated with decreased mortality, while the association between serum cystatin C and increased mortality strengthened. The shapes of the associations in the PREVEND study and NHANES were almost identical.ConclusionsThe strong association between serum creatinine and muscle mass challenges its reliability as GFR marker, necessitating a more cautious approach in its clinical use. The minimal association between serum cystatin C and muscle mass supports its increased use as a more reliable alternative in routine clinical practice.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Creatinine, cystatin C, muscle mass, and mortality: Findings from a primary and replication population‐based cohort

Groothof,

Shehab,

Erler

et al. 2024

J cachexia sarcopenia muscle

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show abstract

“…We thank Groothof et al 1 for their letter and the opportunity to clarify certain aspects of our analysis. 2 In our calculation of eGFR based on creatinine (eGFR cr ), eGFR based on cystatin C (eGFR cys ), and eGFR cr-cys , we followed current recommendations for reporting cystatin C (using two decimals for values in mg/L) and for serum creatinine (using two decimals for values in mg/dl and integers for values in micromole/L).…”

Section: Authors' Reply: Integer Cystatin C Values: Impact On Discord...mentioning

confidence: 99%

Authors' Reply: Integer Cystatin C Values: Impact on Discordance Group Assignment and Accuracy of GFR-Estimating Equations

Fu,

Levey,

Inker

et al. 2023

JASN

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Rounding creatinine, cystatin C or both: impact on discordance group assignment and GFR-estimating equation performance

Cited by 2 publications

References 13 publications

Creatinine, cystatin C, muscle mass, and mortality: Findings from a primary and replication population‐based cohort

Creatinine, cystatin C, muscle mass, and mortality: Findings from a primary and replication population‐based cohort

Authors' Reply: Integer Cystatin C Values: Impact on Discordance Group Assignment and Accuracy of GFR-Estimating Equations

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